# Oral temperature of preweaning dairy heifers: Sensitivity and specificity at detecting individuals with pyrexia

## TL;DR

This study shows that oral temperature can reliably detect fevers in young dairy calves, offering a practical alternative to rectal temperature for health monitoring.

## Contribution

The study validates oral temperature as a feasible and accurate method for fever detection in preweaning dairy calves.

## Key findings

- Oral temperature showed a sensitivity of 79% and specificity of 98% for fever detection.
- Oral and rectal temperatures had a strong positive correlation (r = 0.75).
- An oral temperature threshold of ≥39.1°C was found to be most effective for fever detection.

## Abstract

Summary: Current automated technologies for measuring calf body temperature are limited in their accuracy and practicality in commercial settings. We hypothesized that oral temperature might be a suitable method for body temperature estimation for automated health monitoring. The objective of this study was to validate oral temperature as an alternative to rectal temperature in preweaning dairy calves, particularly for detecting a fever. One hundred fifty calves were followed from 1 to 28 days of life, having oral and rectal temperatures taken every other day. Oral temperature was typically slightly lower than rectal temperature but reliably reflected systemic changes in body temperature and showed very good diagnostic accuracy at fever detection with a sensitivity of 79% and a specificity of 98%. AUC = area under the curve. Graphical abstract created in Canva by the authors. Calf graphic ©elena-istomina via Canva.com, and thermometer graphic ©sketchify, both via Canva.com.

Summary: Current automated technologies for measuring calf body temperature are limited in their accuracy and practicality in commercial settings. We hypothesized that oral temperature might be a suitable method for body temperature estimation for automated health monitoring. The objective of this study was to validate oral temperature as an alternative to rectal temperature in preweaning dairy calves, particularly for detecting a fever. One hundred fifty calves were followed from 1 to 28 days of life, having oral and rectal temperatures taken every other day. Oral temperature was typically slightly lower than rectal temperature but reliably reflected systemic changes in body temperature and showed very good diagnostic accuracy at fever detection with a sensitivity of 79% and a specificity of 98%. AUC = area under the curve. Graphical abstract created in Canva by the authors. Calf graphic ©elena-istomina via Canva.com, and thermometer graphic ©sketchify, both via Canva.com.

•Oral temperature was evaluated for estimating calf body temperature and detecting fever.•Oral temperature showed high diagnostic accuracy with reference to rectal temperature.•Results suggested that oral temperature is an acceptable tool for detecting fever in dairy calves.

Oral temperature was evaluated for estimating calf body temperature and detecting fever.

Oral temperature showed high diagnostic accuracy with reference to rectal temperature.

Results suggested that oral temperature is an acceptable tool for detecting fever in dairy calves.

Change in body temperature can be an early indicator of illness. In calves, body temperature is routinely estimated from rectal temperature measurement. Integrating oral temperature sensors into automated feeding systems might present a feasible alternative to rectal measurement for monitoring calf body temperature. Our objectives were to determine if oral temperature is useful in detecting a fever (rectal temperature ≥39.5°C) and to establish informative oral temperature ranges in dairy calves between 0 and 28 d of life. This diagnostic accuracy study was conducted at one commercial dairy farm in central New York where calves were housed in indoor group pens of 20 calves each with free access to an automated milk feeder. Female Holstein calves (n = 150) were enrolled at birth and followed through 28 d of life. Digital probe thermometers (GLA M700) were used to measure oral and rectal temperatures (10.2 and 5.1 cm probes, respectively) simultaneously at 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 and 28 d of life. Overall mean ± SD (n = 2,081) oral temperature was 38.4°C ± 0.7 and rectal temperature was 38.8°C ± 0.6°C. There was a moderate-to-strong positive correlation (r = 0.75) between oral and rectal temperature. A receiver operating characteristic curve used to evaluate oral temperature in detecting a true fever yielded an area under the curve of 0.91, with a sensitivity of 79% and a specificity of 98% at an oral temperature threshold of ≥39.1°C, as selected by the maximum efficiency index. Our results demonstrate the capability of oral temperature to detect a fever, and that it may be useful for monitoring body temperature changes in preweaning dairy calves. A limitation of our study was that it was conducted in winter and spring with environmental temperatures ranging from −6.7°C to 17.2°C, which mainly fall below calf thermoneutral temperatures (15°C to 25°C). Future work will evaluate the associations of oral temperature with disease and inflammation.